Electrohydraulic actuating device



April 28, 1953 o. GREBE ETAL 2,636,347

ELECTROHYDRAULIC ACTUATING DEVICE Filed July 5, 1950 INVENTORS. O GRE EAND VAL-TE use c PY R S 5 8A H Patented Apr. 28, 1953 UNITED STATESPATENT OFFICE ELECTROHYDRAULIC ACTUATING DEVICE Otto Grebe, Olpe, andWalter Sussebach, Gerlingen, near Olpe, Germany, assignors toElektro-Mechanik G. 111. b. H., Olpe, Germany Application July 5, 1950,Serial No. 172,182 In Germany July 5, 1949 The present invention relatesto an electrohydraulic actuating device, and more particularly to such adevice comprising an electric motor, a pump coupled with the motor and apiston driven by the oil displaced by the pump.

It is an object of the present invention to render the parts easilyinsertable into and removable from the tank holding the oil.

It is another object of the present invention to reduce the overallheight of the electro-hydraulic actuating device.

It is a further object of the present invention to provide anelectro-hydraulic actuating device of the kind described which needsthesmallest possible quantities of material of construction.

It is still another object of the present inven:

tion to provide anelectro-hydraulic actuating device of the kind vdescribed having an entirely closed structure.

It is a still further object of the present invention to provide anelectro-hydraulic actuating device which is sturdy and capable ofresisting heavy loads.

An embodiment according to the present invention comprises an oil tankhaving an end plate, an electric motor arranged in the tank, acentrifugal oil pump arranged in the tank coaxially to the motor andbeing driven by same, a piston arranged for axial displacement in thetank and coaxially to the. motor and the ump and being driven by the oildisplaced by the pump, the motor, the pump and the piston being combinedto a structural unit with the end plate so that they can be insertedinto and removed from the tank as a whole, a stator winding, and arotor, the stator winding and the rotor both forming part of the motorand being arranged for open contact with the oil in the tank so as to besubmerged in oil, whereby the heat generated in the motor is transferredto the oil tank substantially by transfer through the oil.

Preferably a cylinder encloses the piston and is combined to thestructural unit with the motor, the pump and the piston. v

In an embodiment according to the present invention the motor isarranged below the pump and the piston and a bearing plate for the motoris arranged above the motor in the tank, the cylinder enclosing thepistonbeing firmly held between the end plate and the bearing plate;

Preferably the pump is arranged on one end of the shaft of the motor.

According to an embodiment of'the present inventionthe rotorissecuredtoathe shaft of the motor so as to permit an axialdisplacementbetween the rotorandthe shaft.

9 Claims. (CI. 60-52) In an embodiment of the present invention the tankis provided with a lid to which is secured a casing for accommodatingthe terminals for the electric motor.

According to an embodiment of the present invention the piston isbell-shaped and encloses the p mp- According to an embodiment of thepresent invention the side wall of the oil tank is provided with meansfor securing the oil tank to a support.

According to an embodiment of the present invention the piston isprovided with a piston rod extending through the hollow shaft of themotor which is arranged in the tank above the centrifugal oil pump andthe piston.

Preferably a partition is arranged in the tank and thelower bearingplate of the electric motor and the partition form a casing for thepump.

, According to an embodiment of the present invention means are providedfor tightening the stator winding, the bearing plates, the pump casingand the cylinder between the lid and the bottom of the tank. Thesetightening means include preferably fittings arranged in the bearingplates and the bottom for concentrically holding the stator winding, thepump casing and the cylinder. Preferably the fittings for the cylinderare designed asa plurality of concentric grooves for enabling cylindershaving different diameters to be fitted. p

According to an embodiment of the present invention the electric motoris arranged in the lower portionof the tank'and has a substantiallyvertical shaft having an axial boring having an opening at the lower endthereof communicating with the interior of the tank; the piston is holvlowand the pump is mounted in the hollow piston and a solid shaftisconnected to the pump and engages the-boring of the shaft of theelectric motor so as to permit axial displacement of the shafts withrespect to each other. Preferabl the solid shaft has part of squarecross-section which engagesa boring of the shaft of the electric motor..The .novel features which are considered as characteristic for theinvention are set forth in particular inthe appended claims. The inven-\tionxitself, however both as to its construction and itsmethodofoperation, together with addi .tional' objectsand advantages thereof,will be best understood from the following description of specificembodiments when read in connection with the accompanyingdrawing, inwhich the figure is a;sectional elevationof an embodiment of the presentinvention.

Referring now to the drawing an oil tank 10 is shownfwhich encloses allimportant parts of the apparatus. In the lower portion of the tank ii)an electric motor I! is arranged which has a lower bearing plate l2 andan upper bearing plate i3. A centrifugal pump 15 is connected to theshaft 25 of the rotor, the housing of which is formed by a piston l6arranged for axial displacement in the tank It. A piston rod H isconnected to the piston l6 and leads upwards through a gasket H3. Thepiston rod l'i ends in a preferably square piece 23 provided with aneyelet (not shown) for connection to the device to be actuated (notshown). The tank IQ is provided with a casing 43 in which terminals Mare arranged to which the current leads M4 of the stator winding 25 ofthe motor H are connected.

The operation of this device is as follows:

The tank Hi is filled with oil. If the motor I and the pump [5 arestarted the oil is sucked from the space above the piston to the spacebelow the same so that the piston it moves and actuates the device (notshown), such as a brake, a press or the like, connected to the pistonrod H by means of the square end piece 23. If the motor l'! is stoppedthe piston 15 and the pump i5 are axially displaced downwards by theforce of a spring or a weight (not shown) which are tensio ed or lifted,respectively, during the working stroke.

its will be understood from the drawing, not only the pump l5 and thepiston 16 are submerged in oil but also the windings of the motor H Inthis manner local heatings of the windings 25 which'occur for instanceif only one phase of the windings is supplied with current are avoidedor balanced and the overloaded winding is protected against burning. Ifdesired the windings 25 of the motor H can be impregnated with anoil-proof lacquer. If the motor H has a cage armature the cage isprovided with an oil-proof layer of lacquer ortin.

Preferably the resistance of the rotating parts, particularly of; therotor of the motor, against the liquid is so chosen that at a stoppingof the motor the pump is braked as rapidly as possible thereby reducingthe time period which the piston it needs to. return into the initialposition thereof. As a further means for reducing this time period theviscosity of the oil is chosen in dependence on the temperature in sucha manner that at the stationary operating temperature of i the liquid,for instance 17 C., sufiicient resistance of the liquid is left forbraking the rotating parts. Furthermore it is advantageous in many casesto use as a liquid an oil having a high vis-. cosity at low temperaturesso that in starting the motor and the pump an increased frictional loadis generated which heats the oil rapidly to the stationary temperaturethereof.

Preferably the liquid is an oil having a high specific gravity such aschlorinated diphenyl having a specific gravity of approximately 1.5.

The oiltank it! is closed at the lower end thereof and is provided withan end plate or lid 24 at the upper end thereof. The piston I6 moves ina cylinder 38 surrounded by an annular space 31 which is connected byapertures 32 to the space 33 in the upper part of the cylinder 30. Theannular space 31 is connected with the suction side of the pump l5 bymeans of apertures 34. At

' tor ii, the pump 15; the piston l6 and thecyline.

der 39 to the lid 24. As will be seen from the and encloses the pump i5.

drawing the motor is a three-phase motor having three terminals M, andthree leads hi4. In the lower part of the tank it] are arranged threefuses 5!, one for each phase of the windings 25. The fuses are connectedrespectively in series to the stator windings and can be replaced bytemperature-responsive switches. The fuses or temperature-responsiveswitches interrupt the current supply to the windings ii the temperaturethereof exceeds a pre-determined limit.

All essential structural parts such as the motor ii, the pump i5, thepiston 56 and the cylinder 38 are secured to the lid 24 and connected tothe same as a structural unit which can be ini sorted into the oil tankiii and removed from the The piston i6 is bell-shaped It can bedesigned, if desired, so as to enclose in its initial position the motorH as well. The pump I5 is secured to the upper end of the shaft 26 ofthe motor II. If a similar arrangement is provided for the rotor of themotor H the lower bearing plate 12 can be dispensed with and thus theaxial length of the apparatus may be further reduced.

The cylinder 36 is firmly held between the lid 24 and the upper bearingplate IS, the centering of the cylinder being effected by annularfittings it and id, in the lid 2A and the upper bearing plate i3,respectively. If the lid 24 and the bearing plate i3 are provided with aplurality of annular fittings 43', M having diiierent diameters,cylinders, pistons and pumps having difierent diameters can be insertedso that at equal dimensions of the motor and; the oil tank differentactuating forces and times may be accomplished.

If desired the bottom of the oil tank in may be designed as a separatepart and the piston pump motor and the cylinder can be connected to thebottom as a structural unit which can be easily inserted and removed.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofelectro-hydraulic actuating devices diitering from the types describedabove.

While we have illustrated and described the invention as embodied in anelectro-hydraulic actuating device comprising an electric motor, a pumpcoupled with the motor, and a piston driven by the oildisplaced by thepump, we do not intend to be limited to the details shown, since same asa whole.

' various modifications and structural changes may be made withoutdeparting. in any way. from the spirit of my invention.

Without further analysis, the foregoing will so fully reveal the gist ofour invention that others can by applying current knowledge readilyadapt it for various applications without omitting features that, fromthestandpoint of prior art, fairly constitute essentialcharacteristicsof thew generic or specific aspects. of this, inventonand, therefore, such adaptations should and areintended to becomprehended, withinthe meaning and range of; equivalence of thefollowing. claims.

What we claim asnew anddesireto secureby Letters Patent is:

1. An electro-hydraulic actuating device-comprising in combination, anoil tank'having an end. plate; an electric motor arranged insaid tank; acentrifugal oil pump arranged in said tank coaxially .tosaid motorandbeingndlfiyfin by same; a. piston arranged: for axial displacement insaid tank. and coaxially. to saidmotor, andsaid pump and being: drivenby. the oil. displaced by said pump; said motor, said pump and saidpiston being combined to a structural 'unit with said end plate so thatthey can be inserted into and removed from said tank as a whole; astator winding; and a rotor, said stator winding and said rotor bothforming part of said motor and being arranged forfopen contact with theoil in said tank so as to be' submerged in oil, whereby the heatgenerated in said motor is transferred to said oil tank substantially bytransfer through the oil.

with said end plate so that they can be inserted into, and removed fromsaid tank as a whole; a

stator winding; and a rotor, said stator winding H and said rotor bothforming part of said motor and being arranged for open contact with theoil in said tank so as to be submerged in oil, whereby the heatgenerated in said motor is transferred to said oil tank substantially bytransfer through the oil.

3. An electro-hydraulic actuating device comprising in combination, anoil tank having an end plate; an electric motor arranged in said tank; acentrifugal oil pump arranged in said tank coaxially to said motor andbeing driven by same; a piston arranged for axial displacement in saidtank and coaxially to said motor and said pump and being driven by theoil displaced by said pump, said motor being arranged below said pumpand said piston; a bearing plate for said motor arranged above saidmotor in said tank; a cylinder enclosing said piston and firmly heldbetween said end plate and said bearing plate, said motor, said pump,said cylinder and said piston being combined to a structural unit withsaid end plate so that they can be inserted into, and removed from saidtank as a whole; a stator winding; and a rotor, said stator winding andsaid rotor both forming part of said motor and being arranged for opencontact with the oil in said tank so as to be submerged in oil, wherebythe heat generated in said motor is transferred to said oil tanksubstantially by transfer through the oil.

4. An electro-hydraulic actuating device comprising in combination, anoil tank having an end plate; an electric motor having a shaft andarranged in said tank; a centrifugal oil pump arranged at one end ofsaid shaft in said tank coaxially to said motor and being driven bysame; a piston arranged for axial displacement in said tank andcoaxially to said motor and said pump and being driven by the oildisplaced by said pump; said motor, said pump and said piston beingcombined to a structural unit with said end plate so that they can beinserted into, and removed from said tank as a Whole; a stator winding;and a rotor, said stator winding and said rotor both forming part ofsaid motor and being arranged for open contact with the oil in said tankso as to be submerged in oil, whereby the heat generated in said motoris transferred to said oil tank substantially by transfer through theoil.

5. An electro-hydraulic actuating device coma piston arranged for axialdisplacement in said tank and coaxially to said motor and said pump andbeing driven by the oil displaced by said pump, said motor beingarranged below said pump and said piston; a bearing plate for said motorarranged above said motor in said tank;

[a cylinder enclosing said piston and firmly held between said end plateand said bearing plate, said motor, said pump, said cylinder and saidpiston being combined to a structural unit with said end plate so thatthey can'be inserted into,

and removed from said tank as a whole; a stator winding; and a rotor,said stator winding andv "said rotor both forming part of said motorandbeing arranged foropen contact with the oil in said tank so as to besubmerged in oil, whereby the heat generated in said motor istransferred to said oil tank substantially by transfer through. the oil.

An electro-hydraulic actuating device-comprising in combination, an oiltank having a lid; an electric motor arranged in said tank; terminalsfor said electric motor; a casing secured to said lid for accommodatingsaid terminals; a centrifugal oil pump arranged in said tank coaxiallyto said motor and being driven by same; a piston arranged for axialdisplacement in said tank and coaxially to said motor and said pump andbeing driven by the oil displaced by said pump; said motor, said pumpand said piston being combined to a structural unit with said end plateso that they can be inserted into, and removed from said tank as awhole; a stator winding; and a rotor, said stator winding and said rotorboth forming part of said motor and being arranged for open contact withthe oil in said tank so as to be submerged in oil, whereby the heatgenerated in said motor is transferred to said oil tank substantially bytransfer through the oil.

7. An electro-hydraulic actuating device comprising in combination, anoil tank having an end plate; an electric motor arranged in said tank; acentrifugal oil pump arranged in said tank coaxially to said motor andbeing driven by same; a bell-shaped piston enclosing said pump andarranged for axial displacement in said tank and coaxially to said motorand said pump and being driven by the oil displaced by said pump; saidmotor, said pump and said piston being combined to a structural unitwith said end plate so that they can be inserted into and removed fromsaid tank as a whole; a stator winding; and a rotor, said stator windingand said rotor both forming part of said motor and being arranged foropen contact with the oil in said tank so as to be submerged in oil,whereby the heat generated in said motor is transferred to said oil tanksubstantially by transfer through the oil.

8. An electro-hydraulic actuating device, comprising in combination, anoil tank having an end plate; an electric motor arranged in the lowerportion of said tank; a centrifugal oil pump arranged in said tankcoaxially to said motor and being driven by same; a piston arranged foraxial displacement in said tank and coaxially to said motor and saidpump and being driven by the oil displaced by said pump; said motor,said pump and said piston being com-

